A. Field of the Invention
The present invention relates to medical surgical instruments, and in particular, to surgical snare instruments.
B. Problems in the Art
Surgical snares have a wide variety of present uses. Examples are prostrate surgery, removal of tonsils, polyps and other operations where tissue must either be severed and/or removed.
Some examples of surgical snares can be found in the following U.S. patents:
______________________________________ U.S. Pat. No. Inventor Issue Date ______________________________________ 3,828,790 Curtiss, et al. August 13, 1974 3,955,578 Chamness, et al. May 11, 1976 4,256,113 Chamness March 17, 1981 4,294,254 Chamness October 13, 1981 4,326,530 Fleury, Jr. April 27, 1982 4,345,599 McCarrel August 24, 1982 4,493,320 Treat January 15, 1985 4,718,419 Okada January 12, 1988 4,732,150 Keener, Jr. March 22, 1988 ______________________________________
While the above patents reveal a variety of different structures for surgical snares, little or nothing is said about the size ratio of the tube to the wire. Single wire snares illustrated in U.S. Pat. No. 4,732,150 would require a high ratio, because an extremely fine wire would be required to allow contracting the loop inside the cannula without permanent deformation of the wire. An extremely fine wire might be functional in some procedures, however, generally, the fine wire would lack the rigidity necessary to manipulate around and sever or retrieve tissue.
Another concern involves the dual wire snares revealed in the above patents. Dual wires are welded together at one end with the wires parallel. This eliminates the problem of permanent deformation when the loop is pulled into the cannula. However, the shape of the extended loop is extremely limited to a narrow elongated form.
Another undesirable feature of the designs illustrated in the above patents is that the distal ends of the cannulae are cut off square to the axes of the cannulae. This produces a blunt end which is traumatic to insert into an incision or opening.
There is, therefore, a real and significant need for snares that overcome the above objectionable features. It is the primary objective of the present invention to provide a means and method for improved single wire snares which are practical to use in a variety of procedures by virtue of the single snare wire being considerably larger in proportion to the size of the cannula as compared to those illustrated above.
Another object of the present invention is to produce an improved shape to the configuration of the loop in the fully extended and intermediate positions.
Another object of the present invention is to provide a means for less traumatic insertion of the instrument into the incision or opening, and provide a means for both cutting and retrieving tissue.
A still further object of the present invention is to provide a means and method as above described which is simple in structure, durable, efficient, safe, and economical.
These and other objects, features, and advantages of the present invention will become more apparent with reference to the accompanying specification and claims.